Support HIR wf checking for function signatures

During function type-checking, we normalize any associated types in
the function signature (argument types + return type), and then
create WF obligations for each of the normalized types. The HIR wf code
does not currently support this case, so any errors that we get have
imprecise spans.

This commit extends `ObligationCauseCode::WellFormed` to support
recording a function parameter, allowing us to get the corresponding
HIR type if an error occurs. Function typechecking is modified to
pass this information during signature normalization and WF checking.
The resulting code is fairly verbose, due to the fact that we can
no longer normalize the entire signature with a single function call.

As part of the refactoring, we now perform HIR-based WF checking
for several other 'typed items' (statics, consts, and inherent impls).

As a result, WF and projection errors in a function signature now
have a precise span, which points directly at the responsible type.
If a function signature is constructed via a macro, this will allow
the error message to point at the code 'most responsible' for the error
(e.g. a user-supplied macro argument).

19 files changed, 68 insertions, 44 deletions

diff --git a/src/test/ui/associated-types/associated-types-for-unimpl-trait.stderr b/src/test/ui/associated-types/associated-types-for-unimpl-trait.stderr
index e8c11a32bf7..25e80159b0b 100644
--- a/src/test/ui/associated-types/associated-types-for-unimpl-trait.stderr
+++ b/src/test/ui/associated-types/associated-types-for-unimpl-trait.stderr
@@ -1,8 +1,11 @@
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-for-unimpl-trait.rs:10:8
+  --> $DIR/associated-types-for-unimpl-trait.rs:10:40
    |
+LL | trait Get {
+   | --------- required by this bound in `Get`
+...
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) {}
-   |        ^^^^ the trait `Get` is not implemented for `Self`
+   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |
diff --git a/src/test/ui/associated-types/associated-types-no-suitable-bound.stderr b/src/test/ui/associated-types/associated-types-no-suitable-bound.stderr
index e3be434698a..19500f58aa6 100644
--- a/src/test/ui/associated-types/associated-types-no-suitable-bound.stderr
+++ b/src/test/ui/associated-types/associated-types-no-suitable-bound.stderr
@@ -1,8 +1,11 @@
 error[E0277]: the trait bound `T: Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-bound.rs:11:8
+  --> $DIR/associated-types-no-suitable-bound.rs:11:21
    |
+LL | trait Get {
+   | --------- required by this bound in `Get`
+...
 LL |     fn uhoh<T>(foo: <T as Get>::Value) {}
-   |        ^^^^ the trait `Get` is not implemented for `T`
+   |                     ^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `T`
    |
 help: consider restricting type parameter `T`
    |
diff --git a/src/test/ui/associated-types/associated-types-no-suitable-supertrait-2.stderr b/src/test/ui/associated-types/associated-types-no-suitable-supertrait-2.stderr
index 9dc3414e9ed..0e978f20a66 100644
--- a/src/test/ui/associated-types/associated-types-no-suitable-supertrait-2.stderr
+++ b/src/test/ui/associated-types/associated-types-no-suitable-supertrait-2.stderr
@@ -1,8 +1,11 @@
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-supertrait-2.rs:17:8
+  --> $DIR/associated-types-no-suitable-supertrait-2.rs:17:40
    |
+LL | trait Get {
+   | --------- required by this bound in `Get`
+...
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) {}
-   |        ^^^^ the trait `Get` is not implemented for `Self`
+   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |
diff --git a/src/test/ui/associated-types/associated-types-no-suitable-supertrait.stderr b/src/test/ui/associated-types/associated-types-no-suitable-supertrait.stderr
index c2aed3f9de5..1ec3c05983a 100644
--- a/src/test/ui/associated-types/associated-types-no-suitable-supertrait.stderr
+++ b/src/test/ui/associated-types/associated-types-no-suitable-supertrait.stderr
@@ -1,8 +1,11 @@
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-supertrait.rs:17:8
+  --> $DIR/associated-types-no-suitable-supertrait.rs:17:40
    |
+LL | trait Get {
+   | --------- required by this bound in `Get`
+...
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) {}
-   |        ^^^^ the trait `Get` is not implemented for `Self`
+   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |
@@ -10,10 +13,13 @@ LL |     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) where Self: Ge
    |                                                              ^^^^^^^^^^^^^^^
 
 error[E0277]: the trait bound `(T, U): Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-supertrait.rs:22:8
+  --> $DIR/associated-types-no-suitable-supertrait.rs:22:40
    |
+LL | trait Get {
+   | --------- required by this bound in `Get`
+...
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <(T, U) as Get>::Value) {}
-   |        ^^^^ the trait `Get` is not implemented for `(T, U)`
+   |                                        ^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `(T, U)`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/associated-types/associated-types-projection-to-unrelated-trait-in-method-without-default.stderr b/src/test/ui/associated-types/associated-types-projection-to-unrelated-trait-in-method-without-default.stderr
index fb842d96867..b6ee1ed733c 100644
--- a/src/test/ui/associated-types/associated-types-projection-to-unrelated-trait-in-method-without-default.stderr
+++ b/src/test/ui/associated-types/associated-types-projection-to-unrelated-trait-in-method-without-default.stderr
@@ -1,8 +1,11 @@
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-projection-to-unrelated-trait-in-method-without-default.rs:10:8
+  --> $DIR/associated-types-projection-to-unrelated-trait-in-method-without-default.rs:10:40
    |
+LL | trait Get {
+   | --------- required by this bound in `Get`
+...
 LL |     fn okay<U:Get>(&self, foo: U, bar: <Self as Get>::Value);
-   |        ^^^^ the trait `Get` is not implemented for `Self`
+   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |
diff --git a/src/test/ui/const-generics/const_evaluatable_checked/object-safety-err-ret.stderr b/src/test/ui/const-generics/const_evaluatable_checked/object-safety-err-ret.stderr
index e0e6029252c..319e6c2c032 100644
--- a/src/test/ui/const-generics/const_evaluatable_checked/object-safety-err-ret.stderr
+++ b/src/test/ui/const-generics/const_evaluatable_checked/object-safety-err-ret.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `Foo` cannot be made into an object
-  --> $DIR/object-safety-err-ret.rs:17:15
+  --> $DIR/object-safety-err-ret.rs:17:16
    |
 LL | fn use_dyn(v: &dyn Foo) {
-   |               ^^^^^^^^ `Foo` cannot be made into an object
+   |                ^^^^^^^ `Foo` cannot be made into an object
    |
    = help: consider moving `test` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
diff --git a/src/test/ui/error-codes/E0038.stderr b/src/test/ui/error-codes/E0038.stderr
index eb68a6298d1..cead9776e4a 100644
--- a/src/test/ui/error-codes/E0038.stderr
+++ b/src/test/ui/error-codes/E0038.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `Trait` cannot be made into an object
-  --> $DIR/E0038.rs:5:16
+  --> $DIR/E0038.rs:5:20
    |
 LL | fn call_foo(x: Box<dyn Trait>) {
-   |                ^^^^^^^^^^^^^^ `Trait` cannot be made into an object
+   |                    ^^^^^^^^^ `Trait` cannot be made into an object
    |
    = help: consider moving `foo` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
diff --git a/src/test/ui/feature-gates/feature-gate-object_safe_for_dispatch.stderr b/src/test/ui/feature-gates/feature-gate-object_safe_for_dispatch.stderr
index 12195bc1071..c13c05f146a 100644
--- a/src/test/ui/feature-gates/feature-gate-object_safe_for_dispatch.stderr
+++ b/src/test/ui/feature-gates/feature-gate-object_safe_for_dispatch.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `NonObjectSafe1` cannot be made into an object
-  --> $DIR/feature-gate-object_safe_for_dispatch.rs:18:38
+  --> $DIR/feature-gate-object_safe_for_dispatch.rs:18:39
    |
 LL | fn takes_non_object_safe_ref<T>(obj: &dyn NonObjectSafe1) {
-   |                                      ^^^^^^^^^^^^^^^^^^^ `NonObjectSafe1` cannot be made into an object
+   |                                       ^^^^^^^^^^^^^^^^^^ `NonObjectSafe1` cannot be made into an object
    |
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/feature-gate-object_safe_for_dispatch.rs:4:23
@@ -35,10 +35,10 @@ LL |     fn static_fn() where Self: Sized {}
    |                    ^^^^^^^^^^^^^^^^^
 
 error[E0038]: the trait `NonObjectSafe3` cannot be made into an object
-  --> $DIR/feature-gate-object_safe_for_dispatch.rs:27:35
+  --> $DIR/feature-gate-object_safe_for_dispatch.rs:27:39
    |
 LL | fn takes_non_object_safe_box(obj: Box<dyn NonObjectSafe3>) {
-   |                                   ^^^^^^^^^^^^^^^^^^^^^^^ `NonObjectSafe3` cannot be made into an object
+   |                                       ^^^^^^^^^^^^^^^^^^ `NonObjectSafe3` cannot be made into an object
    |
    = help: consider moving `foo` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
diff --git a/src/test/ui/generic-associated-types/gat-in-trait-path.stderr b/src/test/ui/generic-associated-types/gat-in-trait-path.stderr
index eb8e101a83d..8651789688e 100644
--- a/src/test/ui/generic-associated-types/gat-in-trait-path.stderr
+++ b/src/test/ui/generic-associated-types/gat-in-trait-path.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `Foo` cannot be made into an object
-  --> $DIR/gat-in-trait-path.rs:21:13
+  --> $DIR/gat-in-trait-path.rs:21:17
    |
 LL | fn f(_arg : Box<dyn for<'a> Foo<A<'a> = &'a ()>>) {}
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
    |
    = help: consider moving `A` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
diff --git a/src/test/ui/generic-associated-types/issue-67510-pass.stderr b/src/test/ui/generic-associated-types/issue-67510-pass.stderr
index 8cc9f2816a1..b4b89ab0473 100644
--- a/src/test/ui/generic-associated-types/issue-67510-pass.stderr
+++ b/src/test/ui/generic-associated-types/issue-67510-pass.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `X` cannot be made into an object
-  --> $DIR/issue-67510-pass.rs:7:19
+  --> $DIR/issue-67510-pass.rs:7:23
    |
 LL | fn _func1<'a>(_x: Box<dyn X<Y<'a>=&'a ()>>) {}
-   |                   ^^^^^^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
+   |                       ^^^^^^^^^^^^^^^^^^^ `X` cannot be made into an object
    |
    = help: consider moving `Y` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
diff --git a/src/test/ui/generic-associated-types/trait-objects.stderr b/src/test/ui/generic-associated-types/trait-objects.stderr
index a121566bbd8..6429bb8159e 100644
--- a/src/test/ui/generic-associated-types/trait-objects.stderr
+++ b/src/test/ui/generic-associated-types/trait-objects.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `StreamingIterator` cannot be made into an object
-  --> $DIR/trait-objects.rs:10:16
+  --> $DIR/trait-objects.rs:10:21
    |
 LL | fn min_size(x: &mut dyn for<'a> StreamingIterator<Item<'a> = &'a i32>) -> usize {
-   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `StreamingIterator` cannot be made into an object
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `StreamingIterator` cannot be made into an object
    |
    = help: consider moving `Item` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
diff --git a/src/test/ui/issues/issue-18611.stderr b/src/test/ui/issues/issue-18611.stderr
index 8872f51753c..0e942e80e25 100644
--- a/src/test/ui/issues/issue-18611.stderr
+++ b/src/test/ui/issues/issue-18611.stderr
@@ -1,8 +1,11 @@
 error[E0277]: the trait bound `isize: HasState` is not satisfied
-  --> $DIR/issue-18611.rs:1:4
+  --> $DIR/issue-18611.rs:1:18
    |
 LL | fn add_state(op: <isize as HasState>::State) {
-   |    ^^^^^^^^^ the trait `HasState` is not implemented for `isize`
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `HasState` is not implemented for `isize`
+...
+LL | trait HasState {
+   | -------------- required by this bound in `HasState`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-18959.stderr b/src/test/ui/issues/issue-18959.stderr
index 86b530e85a8..2a5416ce85b 100644
--- a/src/test/ui/issues/issue-18959.stderr
+++ b/src/test/ui/issues/issue-18959.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `Bar` cannot be made into an object
-  --> $DIR/issue-18959.rs:11:11
+  --> $DIR/issue-18959.rs:11:12
    |
 LL | fn foo(b: &dyn Bar) {
-   |           ^^^^^^^^ `Bar` cannot be made into an object
+   |            ^^^^^^^ `Bar` cannot be made into an object
    |
    = help: consider moving `foo` to another trait
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
diff --git a/src/test/ui/suggestions/object-unsafe-trait-references-self.stderr b/src/test/ui/suggestions/object-unsafe-trait-references-self.stderr
index 797406f869f..f332b7213d8 100644
--- a/src/test/ui/suggestions/object-unsafe-trait-references-self.stderr
+++ b/src/test/ui/suggestions/object-unsafe-trait-references-self.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `Trait` cannot be made into an object
-  --> $DIR/object-unsafe-trait-references-self.rs:6:11
+  --> $DIR/object-unsafe-trait-references-self.rs:6:12
    |
 LL | fn bar(x: &dyn Trait) {}
-   |           ^^^^^^^^^^ `Trait` cannot be made into an object
+   |            ^^^^^^^^^ `Trait` cannot be made into an object
    |
    = help: consider moving `baz` to another trait
    = help: consider moving `bat` to another trait
@@ -17,10 +17,10 @@ LL |     fn bat(&self) -> Self {}
    |                      ^^^^ ...because method `bat` references the `Self` type in its return type
 
 error[E0038]: the trait `Other` cannot be made into an object
-  --> $DIR/object-unsafe-trait-references-self.rs:10:11
+  --> $DIR/object-unsafe-trait-references-self.rs:10:12
    |
 LL | fn foo(x: &dyn Other) {}
-   |           ^^^^^^^^^^ `Other` cannot be made into an object
+   |            ^^^^^^^^^ `Other` cannot be made into an object
    |
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/object-unsafe-trait-references-self.rs:8:14
diff --git a/src/test/ui/suggestions/object-unsafe-trait-should-use-where-sized.stderr b/src/test/ui/suggestions/object-unsafe-trait-should-use-where-sized.stderr
index a2caf846cc5..4c18f6d79d0 100644
--- a/src/test/ui/suggestions/object-unsafe-trait-should-use-where-sized.stderr
+++ b/src/test/ui/suggestions/object-unsafe-trait-should-use-where-sized.stderr
@@ -1,8 +1,8 @@
 error[E0038]: the trait `Trait` cannot be made into an object
-  --> $DIR/object-unsafe-trait-should-use-where-sized.rs:9:11
+  --> $DIR/object-unsafe-trait-should-use-where-sized.rs:9:12
    |
 LL | fn bar(x: &dyn Trait) {}
-   |           ^^^^^^^^^^ `Trait` cannot be made into an object
+   |            ^^^^^^^^^ `Trait` cannot be made into an object
    |
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
   --> $DIR/object-unsafe-trait-should-use-where-sized.rs:5:8
diff --git a/src/test/ui/wf/wf-foreign-fn-decl-ret.stderr b/src/test/ui/wf/wf-foreign-fn-decl-ret.stderr
index a0eb7d10bd9..f6b48938f9b 100644
--- a/src/test/ui/wf/wf-foreign-fn-decl-ret.stderr
+++ b/src/test/ui/wf/wf-foreign-fn-decl-ret.stderr
@@ -1,8 +1,11 @@
 error[E0277]: the trait bound `(): Foo` is not satisfied
-  --> $DIR/wf-foreign-fn-decl-ret.rs:11:12
+  --> $DIR/wf-foreign-fn-decl-ret.rs:11:25
    |
+LL | pub trait Foo {
+   | ------------- required by this bound in `Foo`
+...
 LL |     pub fn lint_me() -> <() as Foo>::Assoc;
-   |            ^^^^^^^ the trait `Foo` is not implemented for `()`
+   |                         ^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
 
 error[E0277]: the trait bound `u32: Unsatisfied` is not satisfied
   --> $DIR/wf-foreign-fn-decl-ret.rs:14:32
diff --git a/src/test/ui/wf/wf-in-fn-arg.stderr b/src/test/ui/wf/wf-in-fn-arg.stderr
index 9687658feba..ca90e9222de 100644
--- a/src/test/ui/wf/wf-in-fn-arg.stderr
+++ b/src/test/ui/wf/wf-in-fn-arg.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `T: Copy` is not satisfied
-  --> $DIR/wf-in-fn-arg.rs:10:14
+  --> $DIR/wf-in-fn-arg.rs:10:15
    |
 LL | struct MustBeCopy<T:Copy> {
    |                     ---- required by this bound in `MustBeCopy`
 ...
 LL | fn bar<T>(_: &MustBeCopy<T>)
-   |              ^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `T`
+   |               ^^^^^^^^^^^^^ the trait `Copy` is not implemented for `T`
    |
 help: consider restricting type parameter `T`
    |
diff --git a/src/test/ui/wf/wf-trait-default-fn-arg.stderr b/src/test/ui/wf/wf-trait-default-fn-arg.stderr
index c3d5d2b9669..2a129538f76 100644
--- a/src/test/ui/wf/wf-trait-default-fn-arg.stderr
+++ b/src/test/ui/wf/wf-trait-default-fn-arg.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `Self: Eq` is not satisfied
-  --> $DIR/wf-trait-default-fn-arg.rs:11:22
+  --> $DIR/wf-trait-default-fn-arg.rs:11:23
    |
 LL | struct Bar<T:Eq+?Sized> { value: Box<T> }
    |              -- required by this bound in `Bar`
 ...
 LL |     fn bar(&self, x: &Bar<Self>) {
-   |                      ^^^^^^^^^^ the trait `Eq` is not implemented for `Self`
+   |                       ^^^^^^^^^ the trait `Eq` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |
diff --git a/src/test/ui/wf/wf-trait-fn-arg.stderr b/src/test/ui/wf/wf-trait-fn-arg.stderr
index 4510f50feea..7693aa6d2d5 100644
--- a/src/test/ui/wf/wf-trait-fn-arg.stderr
+++ b/src/test/ui/wf/wf-trait-fn-arg.stderr
@@ -1,11 +1,11 @@
 error[E0277]: the trait bound `Self: Eq` is not satisfied
-  --> $DIR/wf-trait-fn-arg.rs:10:22
+  --> $DIR/wf-trait-fn-arg.rs:10:23
    |
 LL | struct Bar<T:Eq+?Sized> { value: Box<T> }
    |              -- required by this bound in `Bar`
 ...
 LL |     fn bar(&self, x: &Bar<Self>);
-   |                      ^^^^^^^^^^ the trait `Eq` is not implemented for `Self`
+   |                       ^^^^^^^^^ the trait `Eq` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |